chemical energy of fuels is directly converted into electrical energy.conventional conversion of chemical energy of fuels into electrical raise steam is then used for spinning turbines connected with electric generators.the efficiency of this,process,which cannot exceed that of a reversible Carnot engine varies from 20 to 40 per cent.Fuel cells,on the other hand convert about 75 per cent of the available chemical energy into electrical energy.fuels cells are associated with number of advantages.their efficiency is very high.About 75 per cent of chemical energy into electrical energy.The individual cells can be stacked and connected in series to generate higher voltages.They are also very light.
However there are a number of engineering problems which shall have to be solved before fuel cells become practical sources of electrical energy.Once it is done.fuel cell technology would bring revolution in the area of energy productions.